﻿// Copyright 2009-2021 Josh Close
// This file is a part of CsvHelper and is dual licensed under MS-PL and Apache 2.0.
// See LICENSE.txt for details or visit http://www.opensource.org/licenses/ms-pl.html for MS-PL and http://opensource.org/licenses/Apache-2.0 for Apache 2.0.
// https://github.com/JoshClose/CsvHelper
using CsvHelper.Configuration;
using CsvHelper.TypeConversion;
using System;
using System.Linq.Expressions;

namespace CsvHelper.Expressions
{
	/// <summary>
	/// Creates primitive records.
	/// </summary>
	public class PrimitiveRecordCreator : RecordCreator
	{
		/// <summary>
		/// Initializes a new instance using the given reader.
		/// </summary>
		/// <param name="reader">The reader.</param>
		public PrimitiveRecordCreator(CsvReader reader) : base(reader) { }

		/// <summary>
		/// Creates a <see cref="Delegate"/> of type <see cref="Func{T}"/>
		/// that will create a record of the given type using the current
		/// reader row.
		/// </summary>
		/// <param name="recordType">The record type.</param>
		protected override Delegate CreateCreateRecordDelegate(Type recordType)
		{
			var method = typeof(IReaderRow).GetProperty("Item", typeof(string), new[] { typeof(int) }).GetGetMethod();
			Expression fieldExpression = Expression.Call(Expression.Constant(Reader), method, Expression.Constant(0, typeof(int)));

			var memberMapData = new MemberMapData(null)
			{
				Index = 0,
				TypeConverter = Reader.Context.TypeConverterCache.GetConverter(recordType)
			};
			memberMapData.TypeConverterOptions = TypeConverterOptions.Merge(new TypeConverterOptions { CultureInfo = Reader.Configuration.CultureInfo }, Reader.Context.TypeConverterOptionsCache.GetOptions(recordType));

			fieldExpression = Expression.Call(Expression.Constant(memberMapData.TypeConverter), "ConvertFromString", null, fieldExpression, Expression.Constant(Reader), Expression.Constant(memberMapData));
			fieldExpression = Expression.Convert(fieldExpression, recordType);

			var funcType = typeof(Func<>).MakeGenericType(recordType);

			return Expression.Lambda(funcType, fieldExpression).Compile();
		}
	}
}
